A method of processing a semiconductor wafer sliced from a monocrystalline ingot comprises at least the steps of chamfering, lapping, etching, mirror-polishing, and cleaning. In the etching step, alkali etching is first performed and then acid etching, preferably reaction-controlled acid etching, is performed. The etching amount of the alkali etching is greater than the etching amount of the acid etching. Alternatively, in the etching step, reaction-controlled acid etching is first performed and then diffusion-controlled acid etching is performed. The etching amount of the reaction-controlled acid etching is greater than the etching amount of the diffusion-controlled acid etching. The method can remove a mechanically formed damage layer, improve surface roughness, and efficiently decrease the depth of locally formed deep pits, while the flatness of the wafer attained through lapping is maintained, in order to produce a chemically etched wafer having a smooth and flat etched surface that hardly causes generation particles and contamination.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of processing a semiconductor wafer sliced from a monocrystalline ingot, said method comprising at least the steps of chamfering, lapping, etching, mirror-polishing, and cleaning, wherein in said etching step reaction-controlled acid etching is first performed and then diffusion-controlled acid etching is performed; and an etching amount of the reaction-controlled acid etching is greater than an etching amount of the diffusion-controlled acid etching.
2. A method of processing a semiconductor wafer according to claim 1 , wherein the etching amount of the reaction-controlled acid etching is 10-30 m, and the etching amount of the diffusion-controlled acid etching is 5-20 m.
3. A method of processing a semiconductor wafer according to claim 2 , wherein in each of the reaction-controlled acid etching and the diffusion-controlled acid etching, there is used an etchant obtained through addition of silicon into a mixed acid aqueous solution composed of hydrofluoric acid, nitric acid, acetic acid, and water, and the silicon concentration of the etchant used in the reaction-controlled acid etching is higher than that of the etchant used in the diffusion-controlled acid etching.
4. A method of processing a semiconductor wafer according to claim 3 , wherein the silicon concentration of the etchant used in the reaction-controlled acid etching is 20-30 g/l, and the silicon concentration of the etchant used in the diffusion-controlled acid etching is 5-15 g/l.
5. A method of processing a semiconductor wafer according to claim 1 , wherein in each of the reaction-controlled acid etching and the diffusion-controlled acid etching, there is used an etchant obtained through addition of silicon into a mixed acid aqueous solution composed of hydrofluoric acid, nitric acid, acetic acid, and water, and the silicon concentration of the etchant used in the reaction-controlled acid etching is higher than that of the etchant used in the diffusion-controlled acid etching.
6. A method of processing a semiconductor wafer according to claim 5 , wherein the silicon concentration of the etchant used in the reaction-controlled acid etching is 20-30 g/l, and the silicon concentration of the etchant used in the diffusion-controlled acid etching is 5-15 g/l.
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February 7, 2001
August 13, 2002
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